U.S. patent application number 14/664986 was filed with the patent office on 2015-09-24 for operating method of vertical heat treatment apparatus, storage medium, and vertical heat treatment apparatus.
The applicant listed for this patent is TOKYO ELECTRON LIMITED. Invention is credited to Kohei FUKUSHIMA, Yutaka MOTOYAMA, Keisuke SUZUKI, Hiromi TAKAHASHI.
Application Number | 20150267293 14/664986 |
Document ID | / |
Family ID | 54141535 |
Filed Date | 2015-09-24 |
United States Patent
Application |
20150267293 |
Kind Code |
A1 |
MOTOYAMA; Yutaka ; et
al. |
September 24, 2015 |
OPERATING METHOD OF VERTICAL HEAT TREATMENT APPARATUS, STORAGE
MEDIUM, AND VERTICAL HEAT TREATMENT APPARATUS
Abstract
An operating method of a vertical heat treatment apparatus which
performs a film forming process by keeping the interior of a
vertical reaction tube surrounded by a heating mechanism at a
vacuum atmosphere and by supplying film forming gases to substrates
accommodated within the reaction tube, includes: performing a film
forming process with respect to the substrates by carrying a
substrate holder holding a plurality of substrates in a shelf form
into the reaction tube; carrying out the substrate holder from the
reaction tube; and carrying a cooling jig into the reaction tube to
cool an inner wall of the reaction tube so as to peel a thin film
adhering to the inner wall of the reaction tube by a thermal stress
and so as to collect the thin film in the cooling jig by
thermophoresis.
Inventors: |
MOTOYAMA; Yutaka; (Oshu-shi,
JP) ; FUKUSHIMA; Kohei; (Oshu-shi, JP) ;
SUZUKI; Keisuke; (Nirasaki City, JP) ; TAKAHASHI;
Hiromi; (Nirasaki City, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TOKYO ELECTRON LIMITED |
Tokyo |
|
JP |
|
|
Family ID: |
54141535 |
Appl. No.: |
14/664986 |
Filed: |
March 23, 2015 |
Current U.S.
Class: |
427/255.28 ;
118/704; 118/729 |
Current CPC
Class: |
C23C 16/4411 20130101;
C23C 16/46 20130101; C23C 16/45546 20130101; C23C 16/4401
20130101 |
International
Class: |
C23C 16/44 20060101
C23C016/44; C23C 16/458 20060101 C23C016/458; C23C 16/455 20060101
C23C016/455; C23C 16/46 20060101 C23C016/46 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 24, 2014 |
JP |
2014-060494 |
Jan 26, 2015 |
JP |
2015-012539 |
Claims
1. An operating method of a vertical heat treatment apparatus which
performs a film forming process by keeping the interior of a
vertical reaction tube surrounded by a heating mechanism at a
vacuum atmosphere and by supplying film forming gases to substrates
accommodated within the reaction tube, comprising: performing a
film forming process with respect to the substrates by carrying a
substrate holder holding a plurality of substrates in a shelf form
into the reaction tube; carrying out the substrate holder from the
reaction tube; and carrying a cooling jig into the reaction tube to
cool an inner wall of the reaction tube so as to peel a thin film
adhering to the inner wall of the reaction tube by a thermal stress
and so as to collect the thin film in the cooling jig by
thermophoresis.
2. The method of claim 1, wherein a purge gas is supplied into the
reaction tube while evacuating the interior of the reaction tube,
when the cooling jig is positioned within the reaction tube.
3. The method of claim 1, wherein processed substrates held in the
substrate holder are interchanged with unprocessed substrates while
the cooling jig is positioned within the reaction tube.
4. The method of claim 1, wherein the cooling jig is a tubular
body.
5. The method of claim 1, wherein T.sub.2 is smaller than T.sub.1
where T.sub.1 is a temperature of an inner wall of a vertical lower
end portion of the reaction tube at a time point when the substrate
holder holding the substrates is completely carried into the
reaction tube and T.sub.2 is a temperature of the inner wall of the
vertical lower end portion of the reaction tube at a time point
when the cooling jig is completely carried into the reaction
tube.
6. The method of claim 5, wherein a distance between the cooling
jig and an inner circumferential wall of the reaction tube is
smaller than a distance between the substrate holder and the inner
circumferential wall of the reaction tube, in a height region
corresponding to 30% or more of a height-direction dimension of the
reaction tube.
7. The method of claim 5, wherein the cooling jig is larger in
thermal capacity than the substrate holder.
8. The method of claim 5, wherein a speed at which the cooling jig
is carried into the reaction tube is higher than a speed at which
the substrate holder is carried into the reaction tube.
9. The method of claim 1, wherein the cooling jig includes a
plurality of protrusions formed on an outer circumferential surface
of the cooling jig opposing an inner circumferential surface of the
reaction tube.
10. The method of claim 9, wherein the cooling jig includes a
cylindrical portion and the protrusions are formed on the
cylindrical portion at a specified interval along a circumferential
direction of the cylindrical portion.
11. A non-transitory computer-readable storage medium which stores
a computer program operating on a computer, wherein the computer
program includes steps organized so as to execute the operating
method of a vertical heat treatment apparatus of claim 1.
12. A vertical heat treatment apparatus which performs a film
forming process by carrying a substrate holder holding a plurality
of substrates in a shelf form into a vertical reaction tube
surrounded by a heating mechanism and by supplying film forming
gases to the substrates, comprising: a cooling jig configured to
cool an inner wall of the reaction tube so as to peel a thin film
adhering to the inner wall of the reaction tube by a thermal stress
and so as to collect the thin film by thermophoresis; and a lift
mechanism configured to carry the substrate holder and the cooling
jig into and out of the reaction tube.
13. The apparatus of claim 12, further comprising: a vacuum exhaust
mechanism configured to evacuate the interior of the reaction tube;
a purge gas supply unit configured to supply a purge gas into the
reaction tube; and a control unit configured to output a control
signal so as to execute the followings: carrying the cooling jig
into the reaction tube by the lift mechanism after processed
substrates are carried out from the reaction tube; and supplying
purge gas into the reaction tube while evacuating the interior of
the reaction tube when the cooling jig is positioned within the
reaction tube.
14. The apparatus of claim 12, wherein the cooling jig is a tubular
body.
15. The apparatus of claim 12, wherein T.sub.2 is smaller than
T.sub.1 where T.sub.1 is a temperature of an inner wall of a
vertical lower end portion of the reaction tube at a time point
when the substrate holder holding the substrates is completely
carried into the reaction tube and T.sub.2 is a temperature of the
inner wall of the vertical lower end portion of the reaction tube
at a time point when the cooling jig is completely carried into the
reaction tube.
16. The apparatus of claim 15, wherein a distance between the
cooling jig and an inner circumferential wall of the reaction tube
is smaller than a distance between the substrate holder and the
inner circumferential wall of the reaction tube, in a height region
corresponding to 30% or more of a height-direction dimension of the
reaction tube.
17. The apparatus of claim 15, wherein the cooling jig is larger in
thermal capacity than the substrate holder.
18. The apparatus of claim 15, wherein a speed at which the cooling
jig is carried into the reaction tube is higher than a speed at
which the substrate holder is carried into the reaction tube.
19. The apparatus of claim 12, wherein the cooling jig includes a
plurality of protrusions formed on an outer circumferential surface
of the cooling jig opposing an inner circumferential surface of the
reaction tube.
20. The apparatus of claim 19, wherein the cooling jig includes a
cylindrical portion and the protrusions are formed on the
cylindrical portion at a specified interval along a circumferential
direction of the cylindrical portion.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of Japanese Patent
Application No. 2014-060494, filed on Mar. 24, 2014 and Japanese
Patent Application No. 2015-012539, filed on Jan. 26, 2015, in the
Japan Patent Office, the disclosure of which is incorporated herein
in their entirety by reference.
TECHNICAL FIELD
[0002] The present disclosure relates to an operating method of a
vertical heat treatment apparatus which performs a film forming
process collectively on a plurality of substrates within a vertical
reaction tube, a non-transitory computer-readable storage medium
which stores the operating method, and a vertical heat treatment
apparatus.
BACKGROUND
[0003] As one example of an apparatus for forming thin films (e.g.,
silicon nitride (SiN) films) on substrates such as semiconductor
wafers (hereinafter referred to as "wafers") or the like, there is
known a batch-type vertical heat treatment apparatus which performs
a film forming process collectively on a plurality of wafers within
a vertical quartz-made reaction tube. As a specific film forming
method using this apparatus, there is employed, e.g., a so-called
ALD (Atomic Layer Deposition) method in which a silicon-containing
source gas and a reaction gas (e.g., an ammonia (NH.sub.3) gas) for
nitriding the source gas are alternately supplied plural times.
Silicon nitride films are formed not only on surfaces of the wafers
but also on outer surfaces of gas injectors for supplying the
respective gases, an inner wall surface of the reaction tube, or
the like.
[0004] However, the silicon nitride films formed on the gas
injectors or the reaction tube are very large in internal stress of
the film and are greatly different in a thermal expansion rate and
a thermal contraction rate from quartz of which the reaction tube
is made. Thus, along with heating and cooling of the reaction tube,
the silicon nitride films are easily separated from the surface of
the gas injectors or the reaction tube. For that reason, if a
process for forming the silicon nitride films is repeated, the
silicon nitride films separated from the surface of the gas
injectors or the reaction tube become particles and adhere to the
wafers. This leads to a reduction of throughput.
[0005] There is known a technique in which adhesion of particles to
wafers is prevented by heating and cooling a reaction container
after silicon nitride films are formed. In this technique, however,
an electric current larger than an electric current used during an
ordinary process is supplied to a heater for heating the interior
of the reaction container. Therefore, the heater is easily
deteriorated (the lifespan of the heater is shortened). Further, in
this case, when cooling the reaction container, a cooling gas
having an extremely low temperature of 0 degrees C. or so is blown
from the outside of the reaction container. For that reason, when
restoring an internal temperature of the reaction container to a
temperature for a process to be subsequently performed, the
internal temperature of the reaction container is difficult to be
stabilized.
[0006] There are known a technique of using two boats, a technique
of evacuating the interior of a reaction chamber when unloading a
boat, and a technique of discharging particles by supplying a purge
gas into a reaction chamber at a large flow rate when loading or
unloading wafers. In these cases, however, it cannot be said that
the techniques are capable of sufficiently suppressing adhesion of
particles to wafers.
SUMMARY
[0007] Some embodiments of the present disclosure provide a
technique capable of suppressing adhesion of particles to
substrates when the substrates are collectively subjected to a film
forming process within a vertical reaction tube.
[0008] According to one embodiment of the present disclosure, an
operating method of a vertical heat treatment apparatus which
performs a film forming process by keeping the interior of a
vertical reaction tube surrounded by a heating mechanism at a
vacuum atmosphere and by supplying film forming gases to substrates
accommodated within the reaction tube, includes: performing a film
forming process with respect to the substrates by carrying a
substrate holder holding a plurality of substrates in a shelf form
into the reaction tube; carrying out the substrate holder from the
reaction tube; and carrying a cooling jig into the reaction tube to
cool an inner wall of the reaction tube so as to peel a thin film
adhering to the inner wall of the reaction tube by a thermal stress
and so as to collect the thin film in the cooling jig by
thermophoresis.
[0009] According to another embodiment of the present disclosure, a
non-transitory computer readable storage medium which stores a
computer program operating on a computer. The computer program
includes steps organized so as to execute the aforementioned
operating method of a vertical heat treatment apparatus.
[0010] According to still another embodiment of the present
disclosure, a vertical heat treatment apparatus which performs a
film forming process by carrying a substrate holder holding a
plurality of substrates in a shelf form into a vertical reaction
tube surrounded by a heating mechanism and by supplying film
forming gases to the substrates, includes: a cooling jig configured
to cool an inner wall of the reaction tube so as to peel a thin
film adhering to the inner wall of the reaction tube by a thermal
stress and so as to collect the thin film by thermophoresis; and a
lift mechanism configured to carry the substrate holder and the
cooling jig into and out of the reaction tube.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate embodiments of
the present disclosure, and together with the general description
given above and the detailed description of the embodiments given
below, serve to explain the principles of the present
disclosure.
[0012] FIG. 1 is a vertical sectional view showing one example of a
vertical heat treatment apparatus according to the present
disclosure.
[0013] FIG. 2 is a horizontal sectional view showing the vertical
heat treatment apparatus shown in FIG. 1.
[0014] FIG. 3 is a vertical sectional view showing one example of
the vertical heat treatment apparatus.
[0015] FIG. 4 is a horizontal sectional view showing the vertical
heat treatment apparatus shown in FIG. 3.
[0016] FIG. 5 is a vertical sectional view showing another example
of the vertical heat treatment apparatus.
[0017] FIG. 6 is a horizontal sectional view showing the vertical
heat treatment apparatus shown in FIG. 5.
[0018] FIG. 7 is a sequence diagram showing one example of a
process performed by the vertical heat treatment apparatus.
[0019] FIG. 8 is a schematic view showing an operation of the
vertical heat treatment apparatus.
[0020] FIG. 9 is a schematic view showing an operation of the
vertical heat treatment apparatus.
[0021] FIG. 10 is a schematic view showing an operation of the
vertical heat treatment apparatus.
[0022] FIG. 11 is a schematic view showing an operation of the
vertical heat treatment apparatus.
[0023] FIG. 12 is a schematic view showing an operation of the
vertical heat treatment apparatus.
[0024] FIG. 13 is a schematic view showing an operation of the
vertical heat treatment apparatus.
[0025] FIG. 14 is a perspective view showing another example of a
cooling jig.
[0026] FIG. 15 is a perspective view showing an example of a rotary
table when the cooling jig has a cylindrical shape.
[0027] FIG. 16 is horizontal sectional view showing when the
cooling jig shown in FIG. 14 is disposed within a reaction
tube.
[0028] FIG. 17 is an explanatory view showing an appearance when
the cooling jig shown in FIG. 14 is disposed within the reaction
tube.
[0029] FIG. 18 is a perspective view showing still another example
of the cooling jig.
[0030] FIG. 19 is a perspective view showing still another example
of the cooling jig.
DETAILED DESCRIPTION
[0031] One example of a vertical heat treatment apparatus according
to an embodiment of the present disclosure will now be described
with reference to FIGS. 1 to 6. In the following detailed
description, numerous specific details are set forth in order to
provide a thorough understanding of the present disclosure.
However, it will be apparent to one of ordinary skill in the art
that the present disclosure may be practiced without these specific
details. In other instances, well-known methods, procedures,
systems, and components have not been described in detail so as not
to unnecessarily obscure aspects of the various embodiments. As
shown in FIG. 1, the apparatus is configured to mount a plurality
of wafers W on a wafer boat 11 as a substrate holder positioned in
a substrate transfer region 1, carry the wafer boat 11 into a
vertical reaction tube 12 installed in a processing region 2
existing above the substrate transfer region 1, and then perform a
film forming process of thin films with respect to the respective
wafers W. In order to prevent the thin film adhering to (formed on)
an inner wall surface of the reaction tube 12 from being generated
as particles 10 and scattering toward the wafers W as will be
described later, a cooling jig (collecting jig) 3 for collecting
the particles 10 is installed at a position laterally spaced apart
from the wafer boat 11 in the substrate transfer region 1. In FIGS.
1 and 2, reference numeral 30 designates a housing which
constitutes an exterior body of the vertical heat treatment
apparatus. Reference numeral 40 designates a mounting stand
disposed outside the housing 30 such that a transportation
container (FOUP) 41 accommodating a plurality of wafers W is placed
on the mounting stand 40.
[0032] Prior to describing an internal structure of the reaction
tube 12 and a specific configuration of the cooling jig 3, details
of individual members disposed in the substrate transfer region 1
will be first described. As shown in FIGS. 1 and 2, a boat elevator
4, which is moved up and down by a lift mechanism 5, is installed
below the reaction tube 12 in the substrate transfer region 1. A
rotation shaft 47, which is rotated about a vertical axis by a
rotating mechanism 49, is installed in the boat elevator 4. In a
top portion of the rotation shaft 47, there is installed a rotary
table 47a on which the wafer boat 11 or the cooling jig 3 is
placed. The boat elevator 4 is provided with a lid 25 for closing a
lower end opening of the reaction tube 12 to be described later. A
heat insulating portion 48 is installed in the lid 25 so as to
surround, e.g., the rotation shaft 47.
[0033] As shown in FIG. 2, at a position laterally spaced apart
from the boat elevator 4, standby regions (standby positions) 11a
and 3a, which are formed of mounting portions for temporarily
supporting the wafer boat 11 and the cooling jig 3, are formed side
by side in a horizontal direction. In this example, the standby
region 11a for the wafer boat 11 is formed adjacent to the boat
elevator 4. The standby region 3a for the cooling jig 3 is formed
at an opposite side of the boat elevator 4 when seen from the
standby region 11a. As shown in FIG. 2, the boat elevator 4, the
standby region 11a and the standby region 3a are arranged side by
side so as to make an arc shape when seen in a plan view. In FIG.
2, reference numeral 30a designates a shielding plate installed
between the standby regions 11a and 3a. A unit (not shown) provided
with a filter and a fan for supplying a clean air to the standby
regions 11a and 3a is disposed at the opposite side of the boat
elevator 4 when seen from the standby regions 11a and 3a. The unit
is not described here.
[0034] As shown in FIG. 2, if an imaginary circle which
interconnects the boat elevator 4, the standby region 11a and the
standby region 3a when seen in a plan view is drawn, a first
transfer mechanism 6 for delivering the wafer boat 11 or the
cooling jig 3 to and from the rotary table 47a on the boat elevator
4 and the standby regions 11a and 3a is installed substantially at
the center position of the imaginary circle. The first transfer
mechanism 6 is configured to move up and down and move toward or
away from the boat elevator 4 and the standby regions 11a and
3a.
[0035] That is to say, at a position spaced apart from the first
transfer mechanism 6 toward an inner wall surface of the housing
30, a lift shaft 31 extending up and down along the longitudinal
direction of the wafer boat 11 is installed as shown in FIGS. 1 and
2. One end of a substantially plate-shaped base portion 32
extending from the lift shaft 31 toward an internal region of the
housing 30 is vertically movably installed in the lift shaft 31.
That is to say, a lift member 32a configured to vertically move
along the lift shaft 31 and provided with a drive unit such as a
motor or the like is installed on the lift shaft 31. One end of the
base portion 32 is connected to the lift member 32a.
[0036] A substantially box-shaped advancing/retreating portion 33,
which moves forward and backward along a rail (not shown)
configured to extend in the longitudinal direction of the base
portion 32, is installed at the other end of the base portion 32. A
plate-shaped rotary plate 34, which rotates about a vertical axis
with respect to the advancing/retreating portion 33, is stacked on
an upper surface of the advancing/retreating portion 33. A rail 34a
extending along a horizontal direction is formed in the rotary
plate 34. An arm 35 capable of advancing and retreating along the
rail 34a is installed on the upper surface of the rotary plate 34.
For example, the rotary table 47a installed on the boat elevator 4
is formed into a circular shape having a diameter smaller than a
diameter of a lower surface of the wafer boat 11 or the cooling jig
3. Therefore, bifurcated tip portions of the arm 35 can be moved to
below the wafer boat 11 or the cooling jig 3. Then, the wafer boat
11 or the cooling jig 3 is supported in a transferrable manner by
moving the arm 35 upward. When the wafer boat 11 or the cooling jig
3 is mounted on the rotary table 47a and in the standby region 11a
or 3a, the arm 35 supporting the wafer boat 11 or the cooling jig 3
is moved down. Subsequently, the arm 35 is retreated.
[0037] A second transfer mechanism 7 for delivering the wafers W
between the transportation container 41 and the wafer boat 11 is
installed above the first transfer mechanism 6 described above. The
second transfer mechanism 7 has substantially the same
configuration as the aforementioned first transfer mechanism 6.
Specifically, the second transfer mechanism 7 includes a base
portion 32, an advancing/retreating portion 33, a rotary plate 34
and a plurality of arms 35. The second transfer mechanism 7 is
configured to move vertically along the lift shaft 31 just like the
first transfer mechanism 6. The second transfer mechanism 7 is
provided with five arms 35 in order to collectively transfer a
plurality of, e.g., five, wafers W. In FIG. 1, for the sake of
simplified illustration, the number of the arms 35 of the second
transfer mechanism 7 is schematically shown. Since arrangement
positions of the first transfer mechanism 6 and the second transfer
mechanism 7 vertically overlap with each other, the second transfer
mechanism 7 is not shown in FIG. 2.
[0038] Next, the wafer boat 11, the cooling jig 3 and internal
members of the reaction tube 12 will be described in detail. The
wafer boat 11 is made of quartz. As shown in FIG. 1, the wafer boat
11 is configured to mount a plurality of, e.g., 150, wafers W in a
shelf form. At upper and lower sides of wafer mounting region of
the wafer boat 11, a top plate 45 and a bottom plate 46 are formed
as parts of the wafer boat 11. The aforementioned first transfer
mechanism 6 is configured to transfer the wafer boat 11 by
supporting the bottom plate 46 from below. When the wafer boat 11
is air-tightly carried into the reaction tube 12, a height position
of the lowermost wafer W among the plurality of wafers W (product
wafers) mounted on the wafer boat 11 is higher than a position of a
lower end portion of the reaction tube 12 by 30% of the height
dimension of the reaction tube 12.
[0039] As shown in FIG. 1, in this example, the cooling jig 3 is
formed into a hollow cylindrical body by quartz. A thickness k of
the cylindrical body is set at, e.g., from 5 mm to 50 mm, such that
the cooling jig 3 becomes larger in heat capacity than the wafer
boat 11 which mounts the wafers W. When seen in a plan view, a
diameter of the cylindrical body is set larger than a diameter of
the wafers W or a diameter of the wafer boat 11 such that an outer
surface of the cooling jig 3 and an inner surface of the reaction
tube 12 are positioned as close as possible when the cooling jig 3
is carried into the reaction tube 12. Specifically, the diameter of
the cylindrical body is set at from 320 mm to 360 mm.
[0040] Next, the internal structure of the reaction tube 12 will be
described. The reaction tube 12 is made of quartz. As shown in FIG.
3, the reaction tube 12 is formed into a substantially cylindrical
shape with a lower surface of the reaction tube 12 opened. Thus,
the wafer boat 11 or the cooling jig 3 is air-tightly carried into
the reaction tube 12 from below. FIGS. 3 and 4 show a state in
which the wafer boat 11 is disposed within the reaction tube 12. A
spaced-apart distance d.sub.1 between the reaction tube 12 and the
wafer boat 11 is set at from 10 mm to 35 mm over a length of the
reaction tube 12. On the other hand, FIGS. 5 and 6 show a state in
which, instead of the wafer boat 11, the cooling jig 3 is disposed
within the reaction tube 12. A spaced-apart distance d.sub.2
between the reaction tube 12 and the cooling jig 3 is set at from 5
mm to 30 mm over the length of the reaction tube 12. Thus, in this
example, the spaced-apart distance d.sub.2 is set smaller than the
spaced-apart distance d.sub.1 over the length of the reaction tube
12. In some embodiments, the relationship between the spaced-apart
distances d.sub.2 and d.sub.1 may be set such that the spaced-apart
distance d.sub.2 becomes smaller than the spaced-apart distance
d.sub.1 over 70% or more of the length of the reaction tube 12.
[0041] As shown in FIGS. 3 and 5, a cylindrical heating furnace
body 14 is installed outside the reaction tube 12 so as to surround
the reaction tube 12. Heaters 13 as heating mechanisms are disposed
on an inner wall surface of the heating furnace body 14 in a
circumferential direction. In FIGS. 3 and 5, reference numeral 16
designates a base plate and reference numeral 18 designates a
manifold which supports the reaction tube 12 from below.
[0042] As shown in FIGS. 4 and 6, when seen in a plan view, one end
portion (front portion) of the reaction tube 12 is expanded outward
over the length of the reaction tube 12, thereby forming a plasma
generating region 12c. An ammonia gas nozzle 51a as a process gas
supply unit (gas injector) extending along the longitudinal
direction of the wafer boat 11 is accommodated in the plasma
generating region 12c. A lower end portion of the ammonia gas
nozzle 51a is air-tightly penetrated through the inner wall surface
of the reaction tube 12 defining the plasma generating region 12c
and is connected to an ammonia gas supply source 55a. As shown in
FIGS. 3 and 5, an end portion of the ammonia gas nozzle 51a
existing at the side of the ammonia gas supply source 55a is
branched in a midway section of the ammonia gas nozzle 51a and is
connected to a supply source 55c of a purge gas such as a nitrogen
(N.sub.2) gas or the like.
[0043] As shown in FIGS. 4 and 6, in order to change an ammonia gas
supplied from the ammonia gas nozzle 51a to plasma, a pair of
plasma generating electrodes 61 and 61 is installed outside the
plasma generating region 12c (outside the reaction tube 12) so as
to interpose the plasma generating region 12c between the plasma
generating electrodes 61 and 61 in the left-right direction. Each
of the plasma generating electrodes 61 and 61 is formed to extend
over the length of the wafer boat 11 and is disposed at a position
adjoining the plasma generating region 12c. A high-frequency power
supply source 64 having a frequency of, e.g., 13.56 MHz, and an
output of, e.g., 1 kW, is connected to the plasma generating
electrodes 61 and 61 through a switch unit 62 and a matcher 63.
[0044] As shown in FIGS. 4 and 6, a source gas nozzle 51b for
supplying a silicon-containing source gas, e.g., a DCS
(dichlorosilane) gas in this example, is disposed at the right side
when seen from the plasma generating region 12c existing at a
position adjoining the wafer boat 11. A lower end portion of the
source gas nozzle 51b is air-tightly penetrated through the inner
wall surface of the reaction tube 12 and is connected to a source
gas supply source 55b. In FIG. 3 and other figures, reference
numeral 52 designates gas ejection holes which are formed in a
corresponding relationship with mounting positions of the
respective wafers W.
[0045] As shown in FIGS. 3 and 5, a cleaning gas nozzle 51c
extending from a supply source 55d of a cleaning gas such as a
hydrogen fluoride (HF) gas, a fluorine (F.sub.2) gas or the like is
air-tightly penetrated through the inner wall surface of the
reaction tube 12 at a position near penetration positions of the
gas nozzles 51a and 51b. A tip portion of the cleaning gas nozzle
51c is opened at a position below the wafer boat 11. In FIGS. 3 and
5, reference numeral 53 designates a valve and reference numeral 54
designates a flow rate control unit. In FIGS. 4 and 6, the cleaning
gas nozzle 51c is not shown.
[0046] A vertically extending rod 50 is disposed within the
reaction tube 12 so as to be located opposite the respective gas
nozzles 51a, 51b and 51c. Temperature detecting units (end portions
of thermocouples) (not shown) for measuring an internal temperature
of the reaction tube 12 are installed on the side surface of the
rod 50. The temperature detecting units are disposed at a plurality
of points along the longitudinal direction of the rod 50.
[0047] As shown in FIGS. 4 and 6, an exhaust port 21 provided with
a tip portion extending in a flange shape and made of quartz is
formed in the reaction tube 12 at a position laterally spaced apart
from the plasma generating region 12c. A vacuum pump 24 as a vacuum
exhaust mechanism is connected through a pressure regulating unit
23, such as a butterfly valve or the like, to an exhaust line 22
extending from the exhaust port 21. In FIGS. 3 and 5, for the sake
of convenience in illustration, the exhaust port 21 is shown at a
position opposing the plasma generating region 12c.
[0048] As shown in FIG. 1, a control unit 100 composed of a
computer for controlling the overall operation of the apparatus is
installed in the vertical heat treatment apparatus. A program for
performing a film forming process to be described later is stored
in a memory of the control unit 100. The program is installed into
the control unit 100 from a storage unit 101 which is a storage
medium such as a hard disk, a compact disk, a magneto-optical disk,
a memory card, a flexible disk or the like.
[0049] Next, a description will be made on an operation of the
aforementioned embodiment, namely an operating method of the
vertical heat treatment apparatus. First, the outline of the
operating method will be described. In the vertical heat treatment
apparatus, as shown at an upper stage in FIG. 7, when a batch
process (film forming process of thin film) for a plurality of
wafers W is repeated plural times, deposits 200 which cause the
generation of particles 10 are removed from an inner wall of the
reaction tube 12 between one batch process and another batch
process subsequent to the one batch process.
[0050] Subsequently, a description will be made on a specific
process performed by the vertical heat treatment apparatus. First,
it is assumed that the wafer boat 11 mounting a plurality of wafers
W has already been air-tightly carried into the reaction tube 12
and further that a film forming process of a thin film (silicon
nitride film) for the respective wafers W has already been started.
Assuming that a start time of the film forming process is "t0", a
temperature of the respective heaters 13 described above is set at
a predetermined temperature T.sub.0 (550 degrees C.), namely a film
forming temperature, at time t0. Accordingly, as shown at a lower
stage in FIG. 7, an actual temperature (detected temperature)
within the reaction tube 12 is set equal to or substantially equal
to the predetermined temperature T.sub.0. The cooling jig 3 is
placed in the standby region 3a.
[0051] Thereafter, when the film forming process for the respective
wafers W is completed at time t1, the silicon nitride films are
formed on the surfaces of the respective wafers W within the
reaction tube 12. As will be described later, the silicon nitride
films are formed by supplying a source gas and a reaction gas into
the reaction tube 12. Therefore, the silicon nitride films as the
deposits 200 are formed not only on the surfaces of the wafers W
but also on gas contacting portions within the reaction tube 12,
such as the inner wall of the reaction tube 12 and the like.
Details of the film forming process performed within the reaction
tube 12 will be described later.
[0052] At time t1 at which the film forming process is completed,
the purge gas is supplied into the reaction tube 12 to restore an
internal atmosphere of the reaction tube 12 to an air atmosphere.
Thereafter, if the wafer boat 11 is moved down, the internal
atmosphere of the reaction tube 12 makes contact with a normal
temperature atmosphere existing below the reaction tube 12. Thus,
the internal atmosphere of the reaction tube 12 is cooled down from
the film forming temperature mentioned above. Then, the wafer boat
11 is moved down to a bottom surface of the substrate transfer
region 1 (time t2). Thereafter, as shown in FIG. 8, the wafer boat
11 is moved to the standby region 11a by the first transfer
mechanism 6, and the cooling jig 3 is transferred to the boat
elevator 4 (the wafer boat 11 and the cooling jig 3 are
interchanged).
[0053] At time t3, the wafer boat 11 transferred to the standby
region 11a and the processed wafers W are subjected to cooling.
That is to say, since the substrate transfer region 1 is kept at
the normal temperature atmosphere, the wafer boat 11 and the
processed wafers W exposed in the normal temperature atmosphere are
naturally cooled. Alternatively, the wafer boat 11 and the wafers W
may be cooled by forcibly spraying a nitrogen gas toward the wafer
boat 11 and the processed wafers W. The wafer boat 11 and the
processed wafers W are actually cooled after time t1 at which they
are taken out from the reaction tube 12. However, for the sake of
convenience in description, it is assumed here that cooling is
started from time t3 at which the wafer boat 11 and the processed
wafers W are placed in the standby region 11a.
[0054] As shown in FIGS. 7 and 9, the cooling jig 3 begins to be
moved up at time t3. At this time, an upward movement speed of the
cooling jig 3 is as high as 300 mm/min to 1,800 mm/min. In this
example, the upward movement speed of the cooling jig 3 is 600
mm/min.
[0055] During the time when the film forming process is performed
with respect to the wafers W, the cooling jig 3 is positioned in
the substrate transfer region 1 kept at the normal temperature
atmosphere. Therefore, a temperature of the cooling jig 3 is lower
than the internal temperature of the reaction tube 12. For that
reason, if a tip portion of the cold cooling jig 3 is moved up to a
position opposing the inner wall surface of the lower end portion
of the reaction tube 12, the inner wall surface of the lower end
portion is cooled to a temperature T.sub.1 (e.g., 350 degrees C.)
by the cooling jig 3 as shown in the lower stage in FIG. 7. In the
meantime, the cooling jig 3 is heated by the reaction tube 12. As
described above, the cooling jig 3 is brought into the reaction
tube 12 at a high speed. Accordingly, it can be said that an outer
circumferential surface of the cooling jig 3 colder than the inner
wall surface of the lower end portion of the reaction tube 12
continues to stay opposite the inner wall surface of the lower end
portion of the reaction tube 12 until the cooling jig 3 is
completely carried into the reaction tube 12.
[0056] As described above, the deposits 200 adhere to the inner
wall surface of the reaction tube 12. As mentioned in the section
of "BACKGROUD", the deposits 200 are large in internal stress and
are larger in thermal expansion rate and thermal contraction rate
than quartz of which the reaction tube 12 is made. For that reason,
the deposits 200 are peeled off from the inner wall surface of the
lower end portion of the reaction tube 12 and tend to stray as
particles 10 within the reaction tube 12.
[0057] However, as shown in FIG. 10, the hot reaction tube 12 is
positioned at one side of the particles 10 while the cold cooling
jig 3 is positioned at the other side of the particles 10 (at the
opposite side from the reaction tube 12). Therefore, the particles
10 are attracted toward the cooling jig 3 by thermophoresis. That
is to say, as shown in FIG. 11, when a hot member and a cold member
are located to be opposite to each other with fine particles such
as the particles 10 or the like interposed between the hot member
and the cold member, gas molecules existing in atmosphere
vigorously move at the side of the hot member while the movement of
the gas molecules is not so vigorous at the side of the cold
member.
[0058] For that reason, the gas molecules collide with the
particles 10 during the movement in the atmosphere. At this time,
kinetic energy of the particles 10 received from hot gas molecules
is higher than a kinetic energy of the particles 10 received from
cold gas molecules. Accordingly, under the atmosphere having such a
temperature gradient, the particles 10 are attracted toward the
cold member (the cooling jig 3) by thermophoresis. Once the
particles 10 adhere to the cooling jig 3, it is difficult for the
particles 10 to be separated from the cooling jig 3 due to, e.g.,
an electrostatic force. Thus, even if the deposits 200 adhere to,
e.g., outer circumferential surfaces of the respective gas nozzles
51a, 51b and 51c, the deposits 200 adhering to the outer
circumferential surfaces of the respective nozzles 51a, 51b and 51c
are removed (collected) by the cooling jig 3 just like the deposits
200 adhering to the inner wall surface of the reaction tube 12.
[0059] After the cooling jig 3 is completely carried into the
reaction tube 12 (after the interior of the reaction tube 12 has
been air-tightly sealed) at time t4, the internal atmosphere of the
reaction tube 12 is substituted as shown in FIG. 12. When
substituting the atmosphere, the interior of the reaction tube 12
is vacuum-drawn into a vacuum state and, then, the purge gas is
intermittently supplied into the reaction tube 12 while keeping the
reaction tube 12 in the vacuum state. A so-called cycle purge which
repeats the vacuum-drawing and the supply of the purge gas plural
times is performed in this way. By substituting the internal
atmosphere of the reaction tube 12, the particles 10 which are not
strongly adsorbed to the inner wall surface of the reaction tube 12
(which are peeled off from the inner wall surface of the reaction
tube 12) or the particles 10 which are not collected by the cooling
jig 3 and are straying within the reaction tube 12 are moved toward
the exhaust port 21. After time t0, electric power is supplied to
the heaters 13 such that the internal temperature of the reaction
tube 12 becomes a predetermined temperature T.sub.0. Thus, as shown
at the lower stage in FIG. 7, the internal temperature of the
reaction tube 12 is increased toward, e.g., the film forming
temperature.
[0060] Thereafter, the substitution of the internal atmosphere of
the reaction tube 12 is completed at time t5. Then, the internal
atmosphere of the reaction tube 12 is restored to the air
atmosphere by the purge gas and the cooling jig 3 is moved down.
Since the lower end opening of the reaction tube 12 is opened, the
internal temperature of the reaction tube 12 is slightly lowered
from the film forming temperature as shown at the lower stage in
FIG. 7. Until time t6 at which the cooling jig 3 is completely
carried out, the cooling of the wafer boat 11 and the processed
wafers W are finished and replacement of the wafers W is performed
by the second transfer mechanism 7 as shown in FIG. 12. That is to
say, the processed wafers W on the wafer boat 11 are returned to an
empty transportation container 41 while unprocessed wafers W are
transferred from an additional transportation container 41 to the
wafer boat 11. In other words, as shown in FIG. 7, the collection
of the particles 10 generated from the inner wall surface of the
lower end portion of the reaction tube 12 and the substitution of
the internal atmosphere of the reaction tube 12 are finished until
time t6 at which the cooling of the wafer boat 11 and the processed
wafers W and the replacement of the wafers W are completed.
[0061] Subsequently, the cooling jig 3 placed on the boat elevator
4 is interchanged with the wafer boat 11 mounting the unprocessed
wafers W. Then, as shown in FIGS. 7 and 13, an upward movement of
the wafer boat 11 is started at time t7. An upward movement speed
of the wafer boat 11 is lower than the upward movement speed of the
cooling jig 3 described above. Specifically, the upward movement
speed of the wafer boat 11 is from 200 mm/min to 500 mm/min. In
this example, the upward movement speed of the wafer boat 11 is 300
mm/min. As mentioned above, the wafer boat 11 is positioned in the
substrate transfer region 1 kept at a normal temperature
atmosphere. Thus, the temperature of the wafer boat 11 is lower
than the internal temperature of the reaction tube 12. For that
reason, as the wafer boat 11 is moved into the reaction tube 12,
the inner wall surface of the reaction tube 12 (especially, the
inner wall surface of the lower end portion of the reaction tube
12) tends to be cooled.
[0062] However, as described above in detail, the upward movement
speed of the wafer boat 11 is lower than the upward movement speed
of the cooling jig 3. Therefore, during the upward movement of the
wafer boat 11, the wafer boat 11 is rapidly heated by the heaters
13. Furthermore, the thermal capacity of the wafer boat 11 is
smaller than that of the cooling jig 3. Therefore, if the wafer
boat 11 is heated by the heaters 13, the temperature of the wafer
boat 11 is rapidly increased. When seen in a plan view, the
spaced-apart distance d.sub.1 between the wafer boat 11 and the
reaction tube 12 is larger than the spaced-apart distance d.sub.2
between the cooling jig 3 and the reaction tube 12. For that
reason, the reaction tube 12 is hardly affected by the temperature
of the wafer boat 11.
[0063] As shown at the lower stage in FIG. 7, a temperature T.sub.2
of the inner wall surface of the lower end portion of the reaction
tube 12 reached by cooling when the wafer boat 11 is carried into
the reaction tube 12 is higher than the temperature T.sub.1 of the
inner wall surface of the lower end portion of the reaction tube 12
reached by cooling when the cooling jig 3 is carried into the
reaction tube 12. Specifically, the temperature T.sub.2 is, e.g.,
400 degrees C. Thus, even if the deposits 200 still adhere to the
inner wall surface of the lower end portion of the reaction tube
12, the deposits 200 do not receive a thermal stress which is
larger than a thermal stress received when the inner wall surface
of the lower end portion of the reaction tube 12 is cooled by the
cooling jig 3. Therefore, the deposits 200 are kept adhered to the
inner wall surface of the lower end portion of the reaction tube
12. That is to say, as described above, the deposits 200 are
greatly different in thermal expansion rate and thermal contraction
rate from the inner wall surface of the reaction tube 12.
Therefore, if cooling and heating are performed while the deposits
200 are kept adhered to the inner wall surface of the reaction tube
12, the deposits 200 tend to be expanded or contracted due to the
thermal stress generated with respect to the inner wall surface of
the reaction tube 12. If the thermal stress grows larger than an
adhesion force of the deposits 200 to the inner wall surface of the
reaction tube 12, the deposits 200 are peeled off (destroyed) into
particles 10.
[0064] Accordingly, it can be said that, even if a thermal stress
smaller than a level at which the adhesion force and the thermal
stress compete with each other is applied to the deposits 200, the
deposits 200 are not separated or hardly separated from the inner
wall surface of the reaction tube 12. In other words, when the
wafer boat 11 is carried into the reaction tube 12, the inner wall
surface of the lower end portion of the reaction tube 12 is cooled
by the wafer boat 11. This may generate particles 10. However, the
particles 10 have already been collected in carrying-in process of
the cooling jig 3. Thus, adhesion of the particles 10 to the wafers
W is prevented. If the wafer boat 11 is air-tightly accommodated
within the reaction tube 12 at time t8, the film forming process
for the wafers W is started. In FIGS. 8, 9, 12 and 13, the reaction
tube 12 and the like are shown in a simplified pattern.
Furthermore, the deposits 200 adhering to the portions other than
the inner wall surface of the reaction tube 12 are not shown.
[0065] Next, a description will be made on one example of a film
forming process performed with respect to the respective wafers W
within the reaction tube 12. In this example, the silicon nitride
films mentioned above are formed by a so-call ALD method in which
different kinds (two kinds) of mutually-reacting gases are
alternately supplied to the wafers W. Specifically, the wafer boat
11 mounting a plurality of unprocessed wafers W is air-tightly
carried into the reaction tube 12. Thereafter, the interior of the
reaction tube 12 is vacuum-drawn. Subsequently, the pressure
regulating unit 23 (an opening degree of the butterfly valve) is
adjusted such that an internal pressure of the reaction tube 12
becomes a processing pressure used when performing the film forming
process. The DCS (dichlorosilane) gas is supplied into the reaction
tube 12. If the DCS gas makes contact with the respective wafers W,
components existing in the DCS gas are adsorbed onto the surfaces
of the wafers W, whereby adsorption layers are formed. As described
above, the adsorption layers are formed not only on the surfaces of
the wafers W but also on the inner wall surface of the reaction
tube 12 and so forth.
[0066] Subsequently, the supply of the DCS gas is stopped and the
interior of the reaction tube 12 is vacuum-drawn. Thereafter, the
purge gas is supplied into the reaction tube 12, thereby
substituting the internal atmosphere of the reaction tube 12. After
the substitution of the internal atmosphere of the reaction tube 12
is performed one or more times, the supply of the purge gas is
stopped. The internal pressure of the reaction tube 12 is set at
the processing pressure. High-frequency power is supplied to the
plasma generating electrodes 61 and 61. Then, an ammonia gas is
supplied from the ammonia gas nozzle 51a to the plasma generating
region 12c. The ammonia gas is converted to plasma by the
high-frequency power supplied to the plasma generating electrodes
61 and 61 and is moved toward the respective wafers W. If the
plasma of the ammonia gas makes contact with the surfaces of the
respective wafers W, the plasma reacts with the adsorption layers
formed on the surfaces of the wafer W or the inner wall surface of
the reaction tube 12. As a result, reaction layers composed of
silicon nitride are formed.
[0067] Thereafter, the supply of the ammonia gas and the supply of
the electric power to the plasma generating electrodes 61 and 61
are stopped and the internal atmosphere of the reaction tube 12 is
substituted. Then, the internal pressure of the reaction tube 12 is
set at the processing pressure. By repeating, plural times, a film
forming cycle in which the DCS gas and the plasma of the ammonia
gas are alternately supplied into the reaction tube 12, a plurality
of reaction layers is laminated one above another. Thus, thin films
composed of silicon nitride films are formed.
[0068] According to the aforementioned embodiment, when the
plurality of wafers W mounted on the wafer boat 11 are collectively
subjected to the film forming process of the silicon nitride films
within the reaction tube 12, the cooling jig 3 differing from the
wafer boat 11 is installed. After the film forming process is
completed, the cooling jig 3 instead of the wafer boat 11 is
carried into the reaction tube 12. The deposits 200 adhering to the
inner wall surface of the reaction tube 12 are peeled off based on
a temperature difference between the cooling jig 3 and the reaction
tube 12. Furthermore, the deposits 200 peeled off from the inner
wall surface of the reaction tube 12 and straying as particles 10
within the reaction tube 12 are caused to adhere to the cooling jig
3 by thermophoresis. Thus, if the wafer boat 11 is carried into the
reaction tube 12 in the subsequent film forming process performed
after collecting the deposits 200, the deposits 200 existing within
the reaction tube 12 are to be peeled off due to the temperature
difference between the wafer boat 11 and the reaction tube 12.
Since the deposits 200 have already been peeled off by the cooling
jig 3, it is possible to suppress adhesion of the particles 10 to
the wafers W.
[0069] The temperature T.sub.2 to which the inner wall surface of
the lower end portion of the reaction tube 12 is cooled when the
cooling jig 3 is carried into the reaction tube 12, is set lower
than the temperature T.sub.3 to which the inner wall surface of the
lower end portion of the reaction tube 12 is cooled when the wafer
boat 11 is carried into the reaction tube 12. Specifically, the
cooling jig 3 is configured to have a thermal capacity larger than
that of the wafer boat 11. Furthermore, the spaced-apart distance
d.sub.2 between the cooling jig 3 and the inner wall surface of the
reaction tube 12 is set smaller than the spaced-apart distance
d.sub.1 between the wafer boat 11 and the inner wall surface of the
reaction tube 12. Moreover, the upward movement speed of the
cooling jig 3 within the reaction tube 12 is set higher than the
upward movement speed of the wafer boat 11 within the reaction tube
12.
[0070] Accordingly, even if the deposits 200 still remain on the
inner wall surface of the reaction tube 12 after the deposits 200
existing in the inner wall surface of the reaction tube 12 are
peeled off by the cooling jig 3, the deposits 200 do not receive a
thermal stress larger than the thermal stress applied by the
cooling jig 3, when the wafer boat 11 is subsequently carried into
the reaction tube 12. Since the thermal stress larger than the
thermal stress applied to the deposits 200 of the inner wall
surface of the reaction tube 12 by the wafer boat 11 is previously
applied to the deposits 200, it is possible to suppress
contamination of the wafers W otherwise caused by the particles
10.
[0071] When the deposits 200 existing in the inner wall surface of
the reaction tube 12 are cooled by the cooling jig 3, only the
deposits 200 or only the portion of the reaction tube 12 near the
deposits 200 is cooled at the inner side of the reaction tube 12
instead of cooling the entirety of the reaction tube 12. The
internal temperature of the reaction tube 12 is uniformly set at
the temperature T.sub.0 during the film forming process. Thus,
since the interior of the reaction tube 12 is rapidly heated to the
film forming temperature T.sub.0 after the deposits 200 are peeled
off, it is possible to rapidly start the subsequent process. That
is to say, in the present disclosure, only a necessary minimum
portion is cooled when peeling the deposits 200 from the inner wall
surface of the reaction tube 12. On the other hand, in the
technique described in the section of "BACKGROUD", the entirety of
the reaction container is cooled at the outer side of the reaction
container. For that reason, a certain period of waiting time is
required in order to subsequently restore the internal temperature
of the reaction container to the film forming temperature. This may
lead to a reduction of throughput.
[0072] The peeling process of the deposits 200 (the collecting
process of the particles 10) using the cooling jig 3 is performed
each time when the batch processes for the wafers W are performed.
It is therefore possible to stably prevent the particles 10 from
being generated throughout the respective batch processes.
Furthermore, the peeling process of the deposits 200 using the
aforementioned cooling jig 3 is performed while performing the
cooling of the processed hot wafers W and the replacement of the
processed wafers W and the unprocessed wafers W. In other words,
the particles 10 are collected in parallel with an ordinary film
forming cycle. Thus, it is possible to prevent the throughput from
being reduced as compared with, e.g., a case where, in order to
prevent the particles 10 from being generated, a film forming
process is first stopped and then resumed after removing the
particles 10.
[0073] In the example described above, the cycle purge (the vacuum
drawing of the interior of the reaction tube 12 and the supply of
the purge gas) is performed after the cooling jig 3 is air-tightly
accommodated within the reaction tube 12. However, the cycle purge
may not be performed. Specifically, the cooling jig 3 may be taken
out immediately just after the cooling jig 3 is air-tightly carried
into the reaction tube 12. Furthermore, as described above in
detail, the particles 10 collected by the cooling jig 3 are
generated in a larger amount from the deposits 200 adhering to a
lower sidewall of the reaction tube 12 than from the deposits 200
adhering to an upper sidewall of the reaction tube 12. Thus, when
carrying the cooling jig 3 into the reaction tube 12, the cooling
jig 3 may be moved up to a height level at which an upper end
surface of the cooling jig 3 is flush with a position of the lower
end portion of the reaction tube 12 or a height level at which an
upper end surface of the cooling jig 3 is a little higher than the
position of the lower end portion of the reaction tube 12. Then,
the cooling jig 3 may be moved down. If the cycle purge is not
performed as mentioned above, it is possible to rapidly finish the
process for removing the deposits 200.
[0074] In some embodiments, "the height level at which the upper
end surface of the cooling jig 3 is a little higher than the
position of the lower end portion of the reaction tube 12" may be a
position higher than the position of the lower end portion of the
reaction tube 12 by 30% of the height dimension of the reaction
tube 12. That is to say, as described above, the lowermost wafer W
is positioned higher in the height direction of the reaction tube
12 than the position of the lower end portion of the reaction tube
12 by 30% of the height dimension of the reaction tube 12.
Accordingly, in order to suppress adhesion of the particles 10 to
any of the wafers W mounted on the wafer boat 11, it is preferable
to previously remove the deposits 200 adhering to the portion of
the reaction tube 12 which is positioned lower than the height
level flush with the lowermost wafer W.
[0075] In the example described above, the relationship between the
temperature T.sub.2 reached by the inner wall surface of the lower
end portion of the reaction tube 12 when the cooling jig 3 is
carried into the reaction tube 12 and the temperature T.sub.3
reached by the inner wall surface of the lower end portion of the
reaction tube 12 when the wafer boat 11 is carried into the
reaction tube 12, is set such that T.sub.2 becomes lower than
T.sub.3. The aforementioned effects can be obtained by setting the
thermal capacity or an external dimension of the cooling jig 3 or
the upward movement speeds of the wafer boat 11 and the cooling jig
3 so as to satisfy the above temperature relationship. However,
T.sub.2 may be equal to T.sub.3. That is to say, it is only
necessary that the deposits 200 which would become particles 10
when the wafer boat 11 is carried into the reaction tube 12 can be
peeled off by the cooling jig 3. For example, if the amount of the
deposits 200 adhering to the inner wall of the reaction tube 12 is
not so much, the relationship between T.sub.2 and T.sub.3 may be
set such that T.sub.2 becomes higher than T.sub.3.
[0076] As the cooling jig 3 described above, it may be possible to
use, e.g., another wafer boat 11 having the same configuration as
the wafer boat 11 for performing the film forming process with
respect to the wafers W. In this case, for example, quartz-made
dummy wafers larger in thickness than the wafers W may be mounted
on the wafer boat 11 for collecting the particles 10, in order to
make sure that the thermal capacity of the wafer boat 11 for
collecting the particles 10 becomes larger than the thermal
capacity of the wafer boat 11 for performing the film forming
process.
[0077] In the example described above, there is employed the method
in which the DCS gas and the plasma of the ammonia gas are
alternately supplied. Alternatively, silicon nitride films may be
formed by a CVD (Chemical Vapor Deposition) method in which the DCS
gas and the ammonia gas are simultaneously supplied into the
reaction tube 12. The thin films formed on the wafers W may not be
silicon nitride films but may be multi-component-based thin films
which are obtained by doping silicon nitride films with boron (B),
oxygen (O) or carbon (C), or thin films such as silicon oxide
(Si--O) films or the like which are composed of a high-k material
as a metal oxide. Taking one example of individual gases used in
forming the silicon oxide films, a silicon-containing organic gas
is used as a source gas, while an oxygen gas or an ozone (O.sub.3)
gas is used as a reaction gas which reacts with the source gas.
Examples of the high-k material may include a hafnium oxide
(Hf--O), an aluminum oxide (Al--O), a zirconium oxide (Zr--O), a
strontium oxide (Sr--O) and a titanium oxide (Ti--O). When forming
films with the high-k material, a source gas containing a metallic
element and an organic substance and an oxidizing gas are used.
[0078] While repeating the batch process with respect to the
plurality of wafers W, the peeling process of the deposits 200 is
performed by the cooling jig 3 each time when the batch process is
performed. Alternatively, the peeling process may be performed
after the batch process is performed plural times. The cooling jig
3 which has collected the particles 10 may be cleaned just like the
wafer boat 11 when cleaning the wafer boat 11 after the
aforementioned batch process is performed plural times.
Specifically, the cooling jig 3 to which the particles 10 adhere is
air-tightly accommodated within the reaction tube 12. Then, a
cleaning gas is supplied into the reaction tube 12 while heating
the interior of the reaction tube 12. By doing so, the particles 10
are etched and are discharged through the exhaust port 21.
[0079] Next, another example of the cooling jig 3 will be
described. The cooling jig 3 may not be the hollow body employed in
the aforementioned embodiment but may be a tubular body with upper
and lower surfaces thereof opened or a tubular body with one of
upper and lower surfaces thereof opened.
[0080] Furthermore, the cooling jig 3 may have a configuration in
which a plurality of protrusions is formed on the outer
circumferential surface of the cooling jig 3 opposing the inner
circumferential surface of the reaction tube 12. FIG. 14 shows one
example of the cooling jig 3 having such a configuration. The
cooling jig 3 of this example includes a cylindrical body 300 and a
plurality of rectangular protrusions 301 formed on an outer
circumferential surface of the cylindrical body 300 at a specified
interval in the circumferential direction. Each of the protrusions
301 extends in the axial direction (up-down direction) of the
cylindrical body 300 and has a substantially quadrilateral cross
section.
[0081] A distance from the surface of each of the protrusions 301
opposing the inner circumferential surface of the reaction tube 12
to the center axis of the cylindrical body 300 is larger than the
radius of the wafer boat 11. Therefore, when the cooling jig 3 is
carried into the reaction tube 12, the distance between the
protrusions 301 and the reaction tube 12 is smaller than the
distance between the wafer boat 11 and the reaction tube 12.
Examples of dimensions of the respective portions of the cooling
jig 3 shown in FIG. 14 are as follows. A height of the cylindrical
body 300 is from 200 mm to 1,000 mm. A height h of the protrusion
301 is from 10 mm to 100 mm. A width d of the protrusion 301 is
from 2 mm to 20 mm. An arrangement pitch of the protrusion 301 (a
gap between width-direction centers of the protrusions 301
adjoining each other) P is from 5 mm to 20 mm. In FIG. 14, for the
sake of convenience in illustration, the protrusions 301 are shown
to have dimensions which do not match with the aforementioned
dimensions.
[0082] For example, as shown in FIG. 15, a rotary table 47a for
holding the cooling jig 3 provided with the cylindrical body 300 is
formed into such a shape that the mutually-opposing peripheral edge
portions of a disc having the same outer diameter as the
cylindrical body 300 are cut away. The dot line indicates a contour
of the disc which is not cut away. Cutaway portions of the disc
become entry regions of the arm 35 for transferring the cooling jig
3.
[0083] FIG. 16 is a horizontal sectional view showing a state in
which the cooling jig 3 shown in FIG. 14 is carried into the
reaction tube 12. In FIG. 16, the distance between the cooling jig
3 and the reaction tube 12 and the dimensions of the protrusions
301 are depicted merely for the sake of convenience and are not
actual dimensions. FIG. 17 is a partially enlarged view showing a
state in which the cooling jig 3 is carried into the reaction tube
12. Since the cooling jig 3 is provided with the protrusions 301,
the distance between the deposits 200 adhering to the reaction tube
12 and the cooling jig 3 differs depending on circumferential
positions when the deposits 200 are seen in a cross-sectional view.
Thus, temperature variations occur. That is to say, a temperature
of portions of the deposits 200 opposing the protrusions 301 is
lower than a temperature of portions of the deposits 200 not
opposing the protrusions 301. For that reason, as indicated by
arrows, stresses acting from high temperature portions toward low
temperature portions are generated. Thus, the peeling of the
deposit is further promoted.
[0084] As mentioned above, the use of the cooling jig 3 provided
with the protrusions 301 is effective. Examples of similar
configurations include cooling jigs 3 shown in FIGS. 18 and 19. The
cooling jig 3 shown in FIG. 18 includes a cylindrical body 300 and
plural rows of vertically-arranged protrusions 302 each having a
dome shape, e.g., a hemispherical shape. The rows of protrusions
302 are arranged in a circumferential direction of the cylindrical
body 300. The cooling jig 3 shown in FIG. 19 is configured by
replacing the dome-shaped protrusions 302 shown in FIG. 18 with
conical protrusions 303. While not shown in the drawings, it may be
possible to use a cooling jig 3 in which the dome-shaped
protrusions 302 shown in FIG. 18 are replaced with rectangular
block-shaped protrusions.
[0085] Dimensions of the respective protrusions 302 and 303 shown
in FIGS. 18 and 19 may be as follows. For example, a height of the
respective protrusions 302 and 303 is from 10 mm to 100 mm. A
diameter of the respective protrusions 302 and 303 at the side of
the cylindrical body 300 (at a root side of the protrusions) is
from 2 mm to 20 mm. An arrangement pitch of the respective
protrusions 302 and 303 is from 5 mm to 20 mm. In case where the
protrusions have a rectangular block shape, a height and an
arrangement pitch are the same as mentioned just above and a width
is, e.g., from 2 mm to 20 mm.
[0086] The types of the protrusions of the cooling jig 3 are not
limited to the aforementioned examples. As an alternative example,
it may be possible to use, e.g., a structure in which ring-shaped
protrusions extending in the circumferential direction of the
cylindrical body 300 are formed at a specified interval in the
vertical direction. In addition, irregularities may be formed by
forming a plurality of concave portions on the outer
circumferential surface of the cylindrical body 300. Even in this
case, the outer circumferential surface of the cylindrical body 300
corresponds to protrusions from the viewpoint of the concave
portions. This means that the protrusions are formed on the
cylindrical body 300.
[0087] According to the present disclosure, when a plurality of
substrates is collectively subjected to the film forming process
within the vertical reaction tube, the cooling jig for peeling
particles from the inner wall of the reaction tube is installed in
addition to the substrate holder for supporting the substrates.
After the film forming process is finished, the substrate holder is
interchanged with the cooling jig positioned in the substrate
transfer region while keeping the internal temperature of the
reaction tube at a predetermined temperature. Thus, the inner wall
surface of the reaction tube is cooled to a low temperature by the
cooling jig. Along with the cooling, the particles peeled off from
the inner wall surface of the reaction tube are adsorbed to the
cooling jig by thermophoresis. Thus, when the film forming process
is subsequently performed with respect to unprocessed substrates,
it is possible to suppress adhesion of particles to the
substrates.
[0088] While certain embodiments have been described, these
embodiments have been presented by way of example only, and are not
intended to limit the scope of the disclosures. Indeed, the
embodiments described herein may be embodied in a variety of other
forms. Furthermore, various omissions, substitutions and changes in
the form of the embodiments described herein may be made without
departing from the spirit of the disclosures. The accompanying
claims and their equivalents are intended to cover such forms or
modifications as would fall within the scope and spirit of the
disclosures.
* * * * *